: >>> shuts off the circuit. We tried today to rewire some things in our : >>> server room, and the GFP kept triggering, and I want help understanding : >>> possible causes. : >>>
: >>> Each server has two power supplies. In an effort to minimize cabling, : >>> we : >>> purchased from Dell some cables that plug into the PDU using Nema
5-15P, : >>> and : >>> split to two different IEC C14 plugs that go to the server power : >>> supplies. : >>> It appears that use of this power cord to two power supplies is what is : >>> causing the ground faults. We can cure the GFP fault simply by leaving : >>> just one of the two plugs in each server. Does someone have an : >>> explanation : >>> as to why the GFP would fault when both power supplies are served from : >>> the : >>> same plug? : >> It might be that the leakage in the PSU's is exceeding the trip : >> current. : >>
: >> In UK (and I think all the EU), RCDs (GFIs) to protect against : >> electrocution are 30mA trip (which means they must trip at : >> somewhere between 15mA and 30mA). General recommendation is that : >> max design leakage is 25% of the trip rating, i.e. 7.5mA. Each : >> piece of Class I (earthed) IT equipment is allowed to leak up : >> to 0.75mA through its RFI components. That gives a maximum of : >> 10 pieces of Class I (earthed) IT equipment per 30mA RCD. In : >> terms of desktop PCs, that's about 5 (each one consisting of : >> a base unit and monitor, which are Class I). (However, we would : >> not normally use RCD protection in server rooms at all.) : >>
: >> Now, all these figures are going to be different in the US : >> and you need to perform a similar calculation. In particular, : >> your GFI's are normally 5mA, which I would imagine is going to : >> severely limit the number of pieces of Class I (earthed) IT : >> equipment per GFI. : >>
: >> -- : >> Andrew Gabriel : >> [email address is not usable -- followup in the newsgroup] : >
: > What he said. Some (most now) power supplies are power factor corrected. : > They have filters that cause a small amount of leakage current to flow on : > the ground. Sum enough of these together and you trip a GFI (or even an RCD : > for really large gear). It appears your two machines each have power : > supplies that are close to tripping the GFI with one power supply connected, : > and will trip when both are connected. : >
: > Charles Perry P.E. : >
: >
: : I wondered about this, is there actually a leakage current or is th : current phase shifted to the extent the GFCI "thinks" there is an imbalance? : : -- : Joe Leikhim K4SAT : "The RFI-EMI-GUY"© : : "Treason doth never prosper: what's the reason? : For if it prosper, none dare call it treason." : : "Follow The Money" ;-P
Actual current.
Charles Perry P.E.